Composition for destroying hardened cementitious mixtures

ABSTRACT

A COMPOSITION FOR DESTROYING HARDENED CEMENTITIOUS MIXTURES COMPRISING METHYL ACETOACETATE AND WATER. A METHOD FOR DESTROYING HARDENED CEMENTITIOUS MIXTURES UTILIZING SAID COMPOSITION IS ALSO COVERED.

United States Patent 3,577,349 COMPOSITION FOR DESTROYING HARDENEDCEMENTITIOUS MIXTURES Robert Glenn Haines, South Charleston, W. Va.,assignor to Union Carbide Corporation, New York, N.Y. No Drawing. FiledJan. 31, 1969, Ser. No. 795,709

Int. Cl. C09d 9/00; Clld 7/05; 023g /02 US. Cl. 252-170 8 ClaimsABSTRACT OF THE DISCLOSURE A composition for destroying hardenedcementitious mixtures comprising methyl acetoacetate and water. A methodfor destroying hardened cementitious mixtures utilizingsaid compositionis also covered.

This invention relates to a novel composition for destroying hardenedconcrete and/ or cement mortars, and to a process for the removal ofhardened concrete and/0r cement mortars from various substrates. l

Concrete builds up on the bafiles and other inside surfaces of concreteready-mix truck drums because of the inability or failure to remove allof the concrete from the ready-mix truck drums before the concretebegins to set-up. Since concrete adheres better to concrete than tosmooth steel, concrete build-up in the ready-mix truck drums enhancesmore concrete build-up. Because of the angle of the baflles inconventional concrete ready-mix truck drums, rotation of the drum in onedirection mixes the drum contents by continuously forcing the upperportion of the contents towards the back or larger closed end of thedrum, whereas rotation of the drum in the opposite direction dischargesthe contents. Any good attempt at washing a ready-mix truck drum byrotating the drum in the mixing direction, if done before the concretesets-up, will clean the backside of the baflles in essentially all ofthe back, larger closed end of the drum. However, the front side of thebaffle, and front, smaller end of the drum can only be cleaned bydiligent and timely use of a high pressure water spray. All ready-mixtrucks have a high pressure water hose with a spray nozzle for thispurpose, but when and how this water is used depends of course, on theindividual operators of the truck. Depending on the slump of theconcrete being hauled (low-slump concrete will form build-up in readymixtruck drums faster than high-slump concrete), a poor truck operator willhave one cubic yard of concrete build-up occur during a period of from 3to 6 months. A good truck operator, i.e., one who regularly andthoroughly cleans the ready-mix drums, may not have this much build-upin more than 3 years. It must be realized, of course, that this morethorough drum cleaning does require operator time which may well resultin an average of one less truck-load per day of concrete delivered. Oncethere is concrete build-up in the truck drum, there are variousconventional ways in which ice it can be removed. Most ready-mixconcrete firms use coarse aggregate and water with drum rotation and/orair hammers to remove the concrete build-up from their truck drums.Other firms, use shaped dynamite charges to destroy the concretebuild-up. Either of these two latter methods, however, can causeconsiderable damage to the drums not to mention the danger involved withthese methods. There are other problem areas in the art wherein concretebuild-up presents problems. For example, concrete build-up is verydetrimental to construction equipment, such as to precast forms, formclamps, mortar boxes, laboratory forms and other tools. The use ofdy-namite charges and other physical means for removing this concretebuild-up in construction equipment is obviously undesirable. Morerecently, the art has relied heavily on chemical compounds and/orcompositions which can be employed as concrete dissolvers. Variousorganic and inorganic compounds have been found to be effective for thispurpose. The inorganic compounds which are useful as concrete dissolversgenerally include inorganic acids such as hydrochloric, phosphoric,hypochlorous and carbonic acid. Salts of these acids and alkalies suchas sodium-hydroxide, sodium bicarbonate and ammoniumsulfate are alsoeifective. The organic chemicals which have been found to be effectiveas concrete dissolvers generally include organic acids such as oxalic,acetic, lactic, citric, tannic and humic acid as well as combinations ofthese acids and other organic compounds such as anhydrides or ethers ofthe above, the most widely used being hydrochloric or muriatic acid. Useof acids whether organic or inorganic for dissolving and/or destroyingcementitious mixtures of course, present safety hazards whereas otherknown compounds although somewhat effective for destroying concrete,unfortunately, also destroy or reduce the desirable properties ofcementitious mixtures even when present in minute, residualconcentrations. It should be remembered that although a chemicalcompound may be effective for destroying concrete, inadvertent, residualconcentrations of it should nevertheless be compatible with new batchesof concrete or cementitious mixtures since there generally remain on thesurface from which the concrete was removed, residual amounts of thechemical compound or dissolver. Thus there is still a need in the artfor a concrete destroyer which is easy to apply, safe to use, and whichpossess properties which do not harmfully affect the properties of newcementitious mixtures such as compressive strength, setting time anddurability.

It is therefore an object of the present invention to provide a novelcomposition for destroying hardened cementitious mixtures such asconcrete and/or cement mortars.

Another object is to provide a process for the removal of hardenedconcrete and/or cement mortars from various substrates. Another objectis to provide a novel composition for destroying hardened concreteinadvertently residual traces of which does not adversely alfect theproperties of newly mixed concrete. These and other objects will beapparent from the following description of the invention.

As employed herein, the term cementitious mixtures is meant to includeconcrete, cement mortars, cinder blocks, masonary mortars, concretelintels, concrete pipe, cementasbestos pipe, prestressed concrete andthe like.

In an effort to provide a hardened cementitious destroyer such as ahardened concrete or mortar destroyer, which is easy to apply, safe touse, and residual traces of which does not affect the properties of newbatches of freshly prepared cementitious mixtures I tried variouscompounds such as: ethylacetoacetate, alpha-chloroethylacetoacetate,ethyl levulinate, methyl levulinate, methyl pyruvate, methyl propionateand methyl chloroacetate. None of these compounds however, were found tobe effective in destroying hardened cementitious mixtures with theexception of ethylacetoacetate which was found to possess a degree ofeffectiveness on very young concrete, i.e., 8 hour old concrete.However, ethylacetoacetate had little or no effect on older concrete,i.e., 24 hour concrete.

During the course of this experimentation, I tried methyl acetoacetate,a compound closely chemically related to the above compounds, and foundsurprisingly, and contrary to normal expectations that the methylacetoacetate was extremely effective in destroying hardened concrete andthis destructive ability was maintained in treating young as well as oldconcrete. Advantageously, it was found that in mixing new batches ofconcrete in equipment previously treated with methyl acetoacetate, thatthe new batches suffered little or no detrimental effects, and in factthere was actually an increase in the compressive strength of the newconcrete which is attributed to the presence of the methyl acetoacetateor more correctly, to the reaction product of methyl acetoacetate andcement.

Broadly contemplated, the present invention provides a composition fordestroying hardened cementitious mixtures which comprises methylacetoacetate and water. More specifically, the composition fordestroying hardened cementitious mixtures comprises from about 60% to99% by Weight methyl acetoacetate, and from about 1 to 40% water.Optionally, though desirably, there can be included in the composition apenetrating aid which has been found to increase the aggressiveness ofthe methyl acetoacetate water solution to the hardened cementitiousmixture.v

The methyl acetoacetate solution can be applied to the surface of thehardened cementitious mixture to be destroyed in any convenient mannerknown in the art. When the hardened cementitious mixture is present onexposed accessible surfaces such as on tools, mortar boxes, clamps,precast forms, and the like, the methyl acetoacetate water solution canbe applied directly to the surface such as by pouring, spraying, dippingand the like. To reach inaccessible enclosed areas, such as the innerarea of a drum of a ready-mix truck, the methyl acetoacetate solution isadded to the enclosed area and the system agitated sufficiently topermit the solution to come in contact with any hardened cementitiousmixture adhering to the drum including the bafiles of the drum.

The methyl acetoacetate-water solution apparently destroys the hardenedcementitious mixture by reacting with the cement phase of the mixture.Application of the methyl acetoacetate to the hardened cementitiousmixture produces a detectable heat of reaction and ultimately thereresults a low-density powder-like solid together with a yellow-orangeliquid product. As a result of the reaction, the chemical composition ofthe cement phase is changed (a portion of the cement phase is actuallysolubilized) and the hardened cementitious mixture is destroyed.

The amount of methyl acetoacetate employed in the methylacetoacetate-Water solution can be varied over a relatively wide rangeand depends in part, upon the age of the hardened cementitious mixtureto be destroyed as well as the length of time available for destruction;Generally, in treating young hardened cementitious mixtures there can beemployed as little as 25% methyl acetoacetate by weight, although higherconcentrations such as 50% and 85% methyl acetoacetate by weight resultsin more destructive power in appreciably shorter periods of time. Merelyas illustrative an 85 weight percent solution of methyl acetoacetatedestroyed a 12 hour old concrete specimen (prepared with limestonecoarse aggregate) in about 3 minutes, whereas 50 and 25 weight percentsolution of methyl acetoacetate required 5 minutes and 40 minutes,respectively, to dissolve similar concrete specimens. Relatively similarresults are achieved in treating older concrete, for example, intreating concrete which was about 17 hours old, with 85, 50 and 25weight percent solutions of methyl acetoacetate, the time required todestroy the concrete was about 65, and 300 minutes respectively. Thus,although some water is necessary for achieving maximum effectiveness indestroying concrete, too much water i.e., substantially more than 15weight percent water merely dilutes and so decreases the rate ofconcrete dissolution. Excellent results are obtained when the methylacetoacetate in the methyl acetoacetate-water solution is in the rangeof about 80 to 90% preferably about by weight of the solution.

Optionally, and desirably, there can be included in the composition, apenetrating aid, which as its name indicates, serves to facilitatecontact of the destroyer solution with the hardened cementitiousmixture. A wide variety of penetrating aids can be employed for thispurpose such as a detergent type penetrating aid of the anionic,non-ionic or cationic type.

Illustrative of the anionic type penetrating aids are the alkyl sulfatesor ethoxy sulfates of secondary alcohols such as the sodium sulfate oftetradecanol; sodium sulfate of 2-methyl 7 ethyl undecanol-4 (Tergitol4); sodium sulfate of 3,9 diethyl tridecan0l-6 (Tergitol 6) and thesodium ethoxysulfate of C to C linear, secondary alcohols (Tergitol15-S-3S).

Illustrative of the non-ionic type penetrating aids are the ethoxylatesof branched secondary alcohols such as the ethoxylate of 2,6,8-trimethyl4 nonanol (Tergitol 15-S-3) and the 9 mol ethoxylate of C to C linear,secondary alcohols ,Tergitol 15-8-9).

Illustrative of a cationic type penetrating aid isl-hydroxyethyl-Z-heptadecenyl glyoxalidine.

The above penetrating aids may be obtained from Union CarbideCorporation under the trademark Tergitol.

The penetrating aid can be added to the composition in an amount of upto about 5 %E by weight preferably about 0.5% by weight based on theweight of the composition.

The methyl acetoacetate to hardened cementitious mixture weight ratiocan also be varied over a relatively wide range as from about 0.01 to 2parts by weight methyl acetoacetate to 1 part by weight hardenedcementitious mixture preferably 0.1 to 1 part by weight methylacetoacetate to 1 part by weight hardened cementitious mixture.

The following examples will illustrate the present invention.

EXAMPLES 1 THROUGH 30 In these examples, the effect of concrete age andmethyl acetoacetate solution concentration on destruction time isillustrated. Static tests were performed on the specimen, i.e., weighedspecimens were immersed in a vessel containing the methyl acetoacetatesolution and the specimens were checked periodically for weight loss. InExamples 1 to 3, the concrete specimens 'were broken concrete testcylinders and in Examples 4 to 30, the concrete specimens were 2" x 2" x2 blocks. The concrete age, concentrations, course aggregate used, andresults are summarized for convenience in Table I below.

TABLE I.-STATIC" TESTS WITH METHYL ACETOACETATE/WATER SOLUTIONS THEEFFECTS OF CON- CRETE AGE AND METHYL ACETOACETATE SOLUTION CONCENTRATIONON DESTRUCTION TIME Methyl aceto- Methyl acetoacetate conc. acetate toCoarse aggregate in solution, concrete wt. used in Example Concrete agewt. percent ratio Time required to destroy concrete concrete 85 1. 1.0hr Limestone. 85 l. 0 Do. 85 1. 0 Do. 85 1. 0 Do. 50 0. Do. 25 0.25 Do.85 1. 0 Ohio river gravel. 50 0. 5 D0. 25 0.25 Do. 85 1. 0 Limestone. 50l). 5 D0. 25 0. 25 Do. 85 1. 0 Ohio river gravel. 50 0. 5 D0. 25 0.25Do. 85 1. 0 37% dissolved in 31 hrs., specimen so Do. 50 0. 5 17%dissolved in 31 hrs.; specimen s0ft Do. 25 0. 25 7% dissolved in 31hrs.; specimen so1id Do. 85 1. 0 3 mins Limestone. 50 0. 5 5 mins Do. 250. 25 40 mins Do. 85 1. 0 85% dissolved in 9 hours Ohio river gravel. 500. 5 22% dissolved in 9 hours Do. 80 0. 25 6% dissolved in 9 hours. Do.80 1. 0 mins Limestone. 50 0. 5 81% dissolved in 129 hours Do. 0. 25 14%dissolved in 129 hours Do. 80 1. 0 38 %dissolved in 71 hours. D0. 50 0.5 18% dissolved in 71 hours Do. 25 0. 25 10% dissolved in 71 hours Do.

TABLE II. ROLLING TESTS WITH METHYL ACETO- EXAMPLES 31 THROUGH 48 Inthese examples, the effect of concrete age and methyl acetoacetatesolution concentration on destruction time utilizing a rolling testprocedure is illustrated. The hardened concrete was located in theinterior of a baffied five gallon steel container into which wasintroduced the methyl acetoacetate solution. Three such baffles eachmeasuring 2 /2 to 3 inches wide of /8 inch steel were welded at a slightangle from vertical to the side of the containers. The concrete formedon and around the baffles. In the rolling test, the chemical solutionwas charged to the bafiled container which contained the concretespecimen, the container lid was clamped in place (the lid had a 1-inchdiameter hole in the center of it) and the container placed on alaboratory roller and rotated continuously at 20 rpm. Periodically, therotation was stopped and the concrete specimen was examined fordeterioration. These rolling tests were continued until the specimen wascompletely dissolved. The concrete age, concentration and results areindicated in Table II.

ACETATE/WATER SOLUTIONS IN BAFFLED, FIVE- GALLON CONTAINERS The effectof concrete age and methyl acetoacetate solution concentration ondestruction time 1 Apparently not enough methyl acetoacetate present.

EXAMPLES 49 THROUGH 52 These examples demonstrate the effect of apenetrating aid for the methyl acetoacetate solution in destroyingconcrete. In Example 50 the penetrating aid employed was Tergitol 7, ananionic detergent (sodium heptadecyl sulfate) available from UnionCarbide Corporation. In Ex ample 51, the penerating aid employed wasTerg-itol TMN a non-ionic detergent (trimethyl nonanol polyethyleneglycol ether) available from Union Carbide Corporation and in Example52, the penetrating aid was Terigtol amine 220, a cationic detergent(hydroxyalkyl alkenyl glyoxalidine). For convenience the characteristicsand results of.the tests are indicated in Table III.

TABLE III.STATIC TESTS: THE EFFECTS OF VARIOUS TYPES OF DETERGENTS ASPENETRATING AIDS FOR METHYL ACETOACETATE IN DESTROYING CONCRETE Concretespecimens: 2" x 2" x 2" concrete cubes. Ohio river gravel coarseaggregate Contact time Ex. Dissolver" solution 1 hour 23 hours 27 hours49.-- Methyl acetoacetate Cube 81% of original weight. Cube 57% oforiginal weight. Reac- Cube 54% of original weight.

tion product a heavy paste. 50"..- Methyl acetoacetate plus 0.5 wt.percent Cube 75% of original weight. Cube 17% of original weight Cubedisintegrated.

TE R GITOL 7 (anionic). I 51 Methyl acetoacetate plus 0.5 wt. percentCube 01 original weight. Cube 16% of original weight Cube 13% oforiginal weight.

TERGITOL TMN (non-ionic). t 52 Methyl acetoacetate plus 0.5 wt. percentCube 84% of original weight. Cube 42% of original welght Cube 41% oforiginal weight.

TE R GITO L AMIN E 220 (cationic).

7 EXAMPLE 53 The example demonstrates the effectiveness of methylacetoacetate and compares its effectiveness with inhibited hydrochloricacid (38 wt. percent). The hydrochloric acid was inhibited with alkylpyridine HB. The test characteristics and results are indicated in TableIV.

85% by weight methyl acetoacetate, about 14.5% water by weight and about0.5% penetrating aid.

3. A composition according to claim 2 wherein said hardened cementitiousmixture is concrete.

4. A process for destroying hardened cementitious mixtures whichcomprises contacting said hardened cementitious mixture, with acomposition consisting essentially of TABLE IV I Contact Weight ratio,pH of time, Chemical W aterChem1cal-Specimens mixtures hours Remarks 4.0 Small pieces falling from specimen. 5. 0 golution ambyer colore .1 l5. peeimen 90 of angina weig 1t. Methyl acetoacetate 25 148 148 6. 4 5Specimen 76 72 or original weight. 7 Specimen 57% of original weight.

2(4). Notling left but paste and stones. Inhibited hydrochloric acid (36wt. percent) 2. 210 790 300 {8 25251323 ZZZ; 33351333153;- (10% H01) 1.O 21 Specimen 81% of original weight.

As will be evident and from the above examples a methyl acetoacetate inan amount of about 60-99% by water solution of methyl acetoacetate isextremely effective as a concrete destroyer and the most effectiveconcentration is an 85/15 weight percent methyl acetoacetate watersolution. The elfectiveness is even more pronounced when a penetratingaid is added to the solution. Although, a water solution of methylacetoacetate is somewhat corrosive, corrosion tests on mild steelindicated that metal lost due to corrosion from the use of methylacetoacetate to dissolve the concrete build-up that occurs in ready-mixconcrete truck drums is not a significant factor in the useful life ofthe drums. This is because the reaction product of methyl acetoacetate,water and concrete is less corrosive to mild steel than water solutionsof methyl acetoacetate. Moreover, no permanent detrimental effects wereobtained in 24 hour immersion (immersion in eighty-five weight percentmethyl acetoacetate-water solutions) tests on neoprene, black rubber,black gum rubber, rubber latex, polyethylene or tygon tubing. Thus, themethyl acetoacetate solution can be employed with tools or equipmentfabricated from these materials.

What is claimed is:

1. A composition for destroying hardened cementitious mixturesconsisting of methyl acetoacetate in an amount of about 60-99% byweight, water in an amount of about 140% by weight and a penetrating aidselected from the group consisting of anionic, nonionic or cationicdetergents in an amount of about 0.5-5% by Weight.

2. A composition according to claim 1 containing about weight and waterin an amount of about 140% by weight for a time sufiicient to destroysaid hardened cementitious mixture.

5. A process according to claim 4 wherein said composition is employedin an amount of about 0.1 to 1% by weight based on the weight of thehardened cementitious mixture.

6. A process according to claim 4 wherein said composition also includesa penetrating aid selected from the group consisting of anionic,nonionic or cationic detergents.

7. A process according to claim 6 wherein said methyl acetoacetate, saidwater and said penetrating aid are employed in an amount of about 14.5%and 0.5% by weight respectively.

8. A process according to claim 7 wherein said hardened cementitiousmixture is concrete.

References Cited Rose: The Condensed Chem. Dict. 6th Ed., Reinhold Publ.cd, 1961, p. 729.

LEON D. ROSDOL, Primary. Examiner W. E. SCHULZ, Assistant Examiner US.Cl. X.R.

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